Gas removing device for electric furnaces



Nov. 16, 1943. L. MICHELAT- GAS REMOVING DEVICE FOR ELECTRIC FURNACES Filed Oct. 28,"l94l 2 Sheets-Sheet 1 Nov. 16, 1943. L. wucr-nzuw GAS REMOVING DEVICE FOR ELECTRIC FURNACES Filed Oct. 28, 1941 2 Sheet s-Sheet 2 5 i/ja 6' I f E l l 6 can Mr Patented Nov. 16, 1943 Leon MichelatFamiers, France; vested in the Custodian Alien Application Ootober as, 1941, Serial No. ucsss In France April 11, 1840 1 AClaims.

One ofthe principal characteristics of electric arc'furnaces utilized in the manufacture of steel is that they constitute an hermetically sealed enclosure. As opposed to the Siemens-Martin type of furnace, where the gases resulting from the re-.

actions during the'processing of the metal go 01! .through chimney-stacks, these gases have no other vent in the electric arc furnace than the charging doors and the openings in the roof provided for the electrodes.

Now, in electric arc furnaces, as nearly perfect gas-tight conditions as possible are sought after, and to this end, it is advisable to obturate the openings for the electrodes by means of flame.

screens and to render the charging doors as hermetic as possible. It consequently seemed contrary to the principles laid down by electric furnace technicians to provide a chimney stack for leading out the gases which are given oil in this type of furnaces, the evacuation of the said gases then taking place to a greater or less extent through the fissures in the various Joints.

These conditions peculiar to the electric arc furnace oifer a serious disadvantage when the processing results in the giving 01 of a large a quantity of gases, especially when molten cast iron is to be charged. The quantity of gases given off is thenso great that the workmen are not allowed to approach the furnace.

Moreover, the applicant has noted that even when the charge is entirely solid, it is profitable, at certain times during the processing, to lacilitate the leading out of the gases and fumes.

Finally, the applicant has also found that a clarification of the atmosphere about the furnace and inside of it, allows a more constant and active supervision of the roof through which the electrodes extend. i

The improvement to electric furnaces which constitutes the object of my invention consists therefore in providing a hole in the roof and in understanding of how my invention can be emmealitis of a cable attached at one end to the framewor The diameter of the stack hole in the roof must be large enough to allow an easy evacuation of the fumes and gaseswhen' the obturator is open and sufficiently small to ensure that, during this period of evacuation, there subsists at the bottom of the charging doors, a slight excess pressure preventing the entrance of air.

- For example, a diameter of about 250 mm. is suitable for a furnace capable of melting 1'7 tons of solid charges.

The following description, in connection with the appended drawings, given by way of example not inclusive of all cases will allow a thorough bodied.

Figure 1 is a vertical sectional view, in diagrammatic form, of an electric furnace provided with the evacuation device.

Figure 2 is a plan view, in diagrammatic form,

of this furnace and showing the position of the setting over the said hole a chimney-stack preferably bent in such a direction with respect to the electrodes that the fumes may be led away from the space occupied by the said electrodes, which stack is provided with a clack valve or obturator that may be opened when it is desired to let off the gases and fumes. U

It is important that this stack does not prevent the movements'. of the roof caused by its thermic expansion or contraction. To this ellect, the staclnis rigidly fixed only to the roof, and to balance-the weight of the bent portion, the latter may be connected to a suitable counterweight by stack with respect to the electrodes. In this figure, 1-]: shows where the sectional view represented in Figure 1 has been taken.

Figure 3 represents on a larger scale and as a partial vertical section taken at III-III in Figure 2, the device for theevacuation of the gases.

The device shown for the evacuation of the gases is constituted by a stack I placed at the key-stone of thefurnace 2, above an orifice Ii especially bored for this purpose in the roof. In the example shown on the drawings, this stack is bent in a direction away from the median electrode 8, as is indicated on Figure 2, so as to prevent the fumes from looking the electrodes 8, 9, l0 and their supports due to corrosion.

The chimney-stack l, the inside of which is lined with refractory pise, rests on the roof of the furnace by means of an intermediate hollow ring eor collar 3, water-filled, the object of whichis to .cool the base of the stack that is to say the portion of the said stack which is exposed to the highest temperature and where the risk of deterioration isthe greatest. The stack is normally closed by a clack-valve! which may be opened at the proper time by operating a cable l2 or by any other means.

The cantilever end of the stack l is connected,

by means of a balancing device ensuring equilibrium, to the fixed framework designated generally by the numeral 1 and which comprises the bar I which supports the brackets lb for the sleeves la, lid of the electrodes, the said crossbar l itself resting on small beams 10 which rest at their ends upon the circular frame member la which forms the peripheral frame-work of the roof. The ends of the beams 1c are connected by the elements M. A guide shoe II, acting as an integral part of the stack can slide vertically in a guide I in fixed to the support I; a cable l4 fixed by one of its extremities to the guide shoe l5 and passing over a sheave l3 mounted on the guide i5a carries at its other end a counterweight 5 balancing the weight of the bent portion of the stack. The said bent portion is thus upheld by the action of the counterweight 5 without the free movement of the stack and, of the roof which carries it being in any way impeded by this arrangement.

In a further effort to allow free vertical movements of translation of the stack in the course of the expansions and contractions of the roof 2, the base 3 of the stack slides freely in a sleeve 8 fixedly connected with the frame I by means of the connected parts ea and 6b.

The device for the leading out of the gases thus constituted offers the following advantages:

1. It allows the efllcient evacuation of the gases through the key-stone, at the proper time, without affecting the stability and the life of the roof.

2. It produces, in the furnace, favorable conditions for the supervision of the room, thanks to the evacuation of the gases and the fumes which clouded the atmosphere of the furnace, prevented a clear vision of the roof through the charging doors I 6 of the furnace and proved harmful to the preservation of the roof.

3. It does not hinder ,the free expansion of the roof and does not affect the insulation between the electrodes.

It is obvious, that without thereby departing from the scope of my invention; it is possible to modify the embodiment which has been described, especially as concerns the shape of the stack and the manner in which it is mounted.

What I claim is:

1. An electric arc furnace comprising a walled enclosure, a roof supported over the said enclosure and free to expand and to contract under the action of variations of temperature, and at least one electrode passing through the said roof, an orifice provided in the roof for the passage of gases and fumes, a chimney stack supported at one of its extremities upon the roof above the said orifice and communicating therewith, said stack comprising, at that one of its extremities which rests on the roof, a hollow wall adapted to be filled with cooling water, and a guide supported on a fixed member of said furnace and surrounding the said hollow wall portion of said stack and adapted to allow the free vertical displace ment of the stack.

2. An electric arc furnace comprising a walled enclosure, aroof supported on the walls of said furnace and above said enclosure and free to expand and to contract under the action of variations of temperature, a framework carried by said roof, at least one electrode passing through the said roof, an orifice provided in the roof for the passage of gases and fumes, a chimney stack supported at one of its extremities upon the roof above the said orifice, the said stack having a bent portion adapted to direct the gases and fumes away from the space occupied by the electrode, a guide for said stack supported on said frame-work and surrounding that extremity of the stack which rests on the roof, said guide being adapted to allow the free vertical movement of the stack, and means comprising a counterweight for balancing the bent portion of the stack, said last means being supported on the frame-work of the roof.

3. An electric arc furnace comprising a walled enclosure, a roof supported upon the walls of said enclosure and being free to expand and to contract under the influence of the heat of the furnace, at least one electrode passing through said roof, an orifice in said roof for the passage of gases and fumes therethrough. a chimney stack supported entirely by said roof, means carried by said roof for thus supporting said stack, said stack having its lower end applied to said orifice and communicating therewith for the eduction of said gases and fumes, and separate means also supported by said roof for centering and guiding the stack with respect to said orifice while otherwise permitting free displacement thereof in the course of the expansions and contractions of the roof.

4. An electric arc furnace comprising a walled enclosure, a roof supported-upon the walls of said enclosure and being free to expand and to contract under the influence of the heat of the furnace, at least one electrode passing through said roof, an orifice in said roof for the passage of gases and fumes therethrough, a chimney stack supported entirely by said roof and having its lower end applied to said orifice and communicating therewith for the eduction of said gases and fumes, said stack having a bent, portion adapted to direct the gases and fumes away from the vicinity of the electrodes, means for supporting said stack at said bent portion from the roof for free substantially vertical movement under the influence of the expansion and contraction of the furnace, and means for centering and guiding said lower end of the stack with respect to said orifice in the course of such movement.

LEON mcrmna'r. 

